A process of making paper and paper made therefrom using starch anthranilate

ABSTRACT

A method of improving the properties of treated paper by addition of starch anthranilate to paper pulp and paper made therefrom. More particularly, the invention covers the use of starch anthranilate in improving the retention of inorganic filler and fiber fines in the processing of paper. Various other properties of the formed paper article are also improved such as dry strength and tensile strength.

United States Patent Inventor Stanley Marshall Parmerter Wheaton, Ill.

App]. No. 16,245

Filed Mar. 3, I970 Patented Nov. 16, 1971 Assignee CPC International Inc.

Englewood, Calif.

Continuation-impart of application Ser. No. 676,614, Oct. 19, 1967, now abandoned. This application Mar. 3, 1970, Ser. No. 16,245

A PROCESS OF MAKING PAPER AND PAPER MADE THEREFROM USING STARCH ANTHRANILA'I'E 8 Claims, No Drawings US. Cl 162/175, 127/32, 162/181 A, 260/233.5

Int. D2lb 3/28 Fieldoiseardl 162/175;

References Cited UNITED STATES PATENTS 2,461,139 2/1949 Caldwell 260/2335 3,499,886 3/1970 Mehltretter 260/2335 3,511,830 5/1970 Speakman 260/233.5

Primary Examiner-S. Leon Bashore Assistant ExaminerFrederick Frei Attomeys-Frank E. Robbins, Joseph Shekleton, Janet E.

Price, Robert D. Weist, Martha A. Michaels and Dorothy R. Thumler A PROCESS OF MAKING PAPER AND PAPER MADE THEREFROM USING STARCH ANTHRANILATE This application is a continuation-in-part of US. Ser. No. 676,614, filed Oct. 19, 1967, and now abandoned.

Paper is manufactured for the most part from woodpulp. A small amount of high-grade paper is manufactured from rag pulp. There are five different kinds of woodpulp: mechanical pulp (ground wood), semichemical pulp, sulfite pulp, sulfate or kraft pulp, and soda pulp. The first is prepared by purely mechanical means, the second by a combination of mechanical and chemical means and the other three by chemical means. The mechanical pulp contains substantially all the wood except the bark and that lost during storage and transportation. Semichemical pulps are partially free of lignin. Chemical pulps, however, are essentially cellulose, the unwanted lignin and other noncellulosic components of the wood having been dissolved away by the cooking and bleaching treatment. Because of this, chemical pulps are much superior to mechanical and semichemical pulps for fine papermaking. However, because of the special processing required, they are too expensive to serve as the main source of fiber for the cheaper grades of paper such as newsprint.

lfthe pulp fibers were the only constituents of a paper sheet, the usefulness of the paper would be very restricted because the sheet would be soft, have a yellowish color, and could not be successfully written or printed upon with ink. If the sheet were thin, it would be transparent to matter printed upon the opposite side. it is necessary, then, to add other substances, such as sizing or coloring agents, and fillers to the cellulosic fibers to produce paper suited to its many uses.

Many papers, except the absorbent types, filter papers and most packaging papers, must have a finely ground filler added to them, the purpose of which is to occupy the spaces between the fibers-thus giving a smooth surface, a more brilliant whiteness, improved printability and improved opacity. The fillers are inorganic substances and may be either naturally occurring materials such as talc, agalite, pearl filler, barytes and certain clays, such as china clay, or artificial fillers, such as suitably precipitated calcium carbonate, crown filler (pearl hardening), blanc fixe, and titanium dioxide pigments. Sizing is added to the paper, other than absorbent papers and filter paper, to impart resistance to penetration by liquids. Common sizing agents added to the pulp before it is formed into a sheet are wax emulsions or soaps made by the saponification of 5 rosin with alkali. The sizes are precipitated with alum.

Pulp stock is prepared from formation into paper by two general processes, beating and refining. Mills use either one or the other alone or both together. The most generally used type of heater is that known as the Hollander. Beating the fibers makes the paper stronger, more uniform, more dense, and less porous. It is in the beater that fillers, coloring agents and sizing agents may be added. The standard practice in making the finer grades of paper is to follow the beaters with the refiners.

While the usual practice is to add filler, sizing and coloring agents to the beaters, they may be added prior to the Jordan or to a combination of points in the system or subsequent to the beating operation but prior to the refining step, as for example, prior to beating. The order in which the materials are added to the beaters may vary with different mills. Generally, however, the filler is first added to the blended pulp, and afier sufficient beating, the sizing and coloring reagents are added. In some instances, all or part of the sizing is surface applied to the formed, dried sheet, using animal glues, starches, or gelatin as the sizing. Again, alum is most generally added to the beater, but in some mills, this practice is varied, and the pulp may be treated with this chemical during the refining step or even layer in the paper-processing scheme.

The machines used for the actual formation of the paper sheet are of two general types, the Fourdrinier machine and the cylinder machine. The basic principles of operation are essentially the same for both machines. The sheet is formed on a travelling bronze screen or cylinder, dewatered under rollers, dried by heated rollers and finished by calendar rolls. In the Fourdrinier machine, the stock of the foregoing operations is sent to the headbox from which it flows onto a moving, endless bronze wire screen. The pulp fibers remain on the screen while a greater proportion of the water, containing unretained fiber fines and unretained filler drains through. As the Fourdrinier wire moves along, it has a sidewise shaking motion which serves to orient some of the fibers and give better felting action and more strength to the sheet. While still on the Fourdrinier wire, the paper passes over suction boxes to remove water and under a dandy roll which smoothes the top of the sheet. In the cylinder machine, there are several parallel vats into which similar or dissimilar paper stocks are charged. A wire-covered rotating cylinder rotates in each vat. The paper stock is deposited on the turning screens as the water inside the cylinder is removed. As the cylinder revolves further, the paper stock reaches a point where the wet layer comes into contact with and adheres to the moving felt. This felt and paper, after removal of some of the water, comes into contact with the top of the next cylinder and picks up another layer of wet paper. Thus, a composite wet sheet or board is built up and passes through press rolls onto the drying and smoothing rolls.

in an attempt to improve filler and fiber fines retention in the paper-manufacturing operation chemical additives are incorporated with the paper stock before it reaches either the cylinder vat or the Fourdrinier wire. These additives, for the most part, have not been entirely satisfactory from several operational points of view. One of the chief drawbacks of most chemicals used to improve filler and fiber fines retention in manufacture of paper is that they must possess certain characteristics and properties which are extremely difficult to achieve in any particular chemical. For instance, the particular chemical used should not be affected by other additives normally used in the paper-processing operation such as rosin size, alum, sodium aluminate, clays and the like. Also important for a particular additive to be effective for improving retention is that it must not be afi'ected by variations in pH. Similarly, the ideal additive chemical should not be affected by the particular electrokinetic charge on the cellulose fibers and fine. The use of a chemical, of course, must be such that it does not have any adverse effects on the finished sheet and it should be relatively safe to handle.

in addition to possessing the above desirable characteristics an additive for improving filler and fines retention must be capable of acting both upon the filler and fines in the system to efficiently cause both materials to be retained in the finished sheet, rather than causing one to be preferentially acted upon. Another important characteristic is that it must be capable of operating on a large variety of stocks.

Also of importance in the election of the fines and filler retention agent is that it must not affect dyestuffs which are frequently used for coloring agents and various types of paperstocks. It also must not interfere with the beneficial effects imparted to paperstocks by coatings which are frequently placed on different types of paper during its manufacture.

Many prior art filler and fiber fines retention aids fail to achieve the above desired objects. In addition, certain of these known retention additives cannot be employed in effective combinations with various fillers or other paper additives. Often times efficiency is low except when gross, uneconomical amounts are added. Adverse effects upon the finished paper product are noted with some prior art retention aids which cause poor dispersibility of the other system additives with resultant localized nonuniform areas. Lastly, many additives fail to operate as desired by promoting filler trapage on the top side of the fiber material.

It would therefore be an advance in the art if an additive were discovered which had an acceptable activity in retaining filler and fiber fines. MOreover, if retention could be promoted without imparting detrimental side effects, and loss of other desirable properties of the type noted above and others, the additive in question would find ready acceptance in the art. If, on the other hand, properties of the finally formed paper article, such as dry strength and tensile strengths were improved by means of addition of the retention aid, this would be an extra economical benefit to be gained through use of an additive of this type.

It, therefore, becomes an object of the invention to provide a new and improved method for improving filler and fines retention in the manufacture of paper by addition of a specific additive to the pulp during the paper processing.

A further object is to provide an agent of this type to improve filler and fines retention which is effective at low economical dosages, will not interfere with other additives and substances used in the makeup and manufacture of the paper, and which will have no adverse effects on the chemical and physical characteristics of the finished sheet.

Yet another object of the invention is to provide a retention additive which when used in combination with alum gives especially improved retention efiects.

An important object of the invention is to provide an additive for improving filler and fines retention in manufactured paper which will operate on a wide variety of paper stocks, is safe to handle, and will impart to the finished sheet certain and desirable characteristics which have not heretofore been available when prior attempts have been made to use other chemicals as fines and filler retention aids.

A special object of the invention is to provide a method of improving filler and fines retention in manufacturing paper by addition of a specific chemical additive, which additive also imparts to the finished paper article improved tensile and dry strengths.

Other objects will appear hereinafter In accordance with the invention it has been discovered that starch anthranilates have excellent activity in promoting filler and fiber fines retention in paper making processes. The starch derivatives show a retention activity even at addition levels as low as 2 pounds per ton based on the weight of the total pulp (0.1 percent by weight), have acceptable water solubility, and may be used as retention aids for all fiber furnishes, including both bleached and unbleached primary virgin chemical pulps, mechanical pulps, and secondary fibers, that is, fibers previously employed as paper stock, and rag pulps. As much as pounds of starch anthranilate per ton of pulp may be employed without departing from the scope of the invention.

Thestarch anthranilate (starch ester of anthranilic acid or o-aminobenzoic acid) may be formed by a number of techniques involving reaction of the hydroxyl groups of the starch with appropriate molecules.

The starch reactant itself that may be used in practicing the invention may be derived from any vegetable source, such as, for example, corn, wheat, potato, tapioca, rice, sago and grain sorghum. The term starch" is used broadly herein and encompasses unmodified starch and tailings, and as well, starch that has been modified somewhat by treatments with acids, a1- kalis, enzymes or oxidizing agents. Soluble or partially soluble modified starches, dextrins, pregelatinized products, and already derivatized starches are also suitable for use in the process. If the starting starch material is already derivatized in some manner, it nevertheless is useful as long as the product is still essentially amylaceous in nature and still contains hydroxyl groups capable of reacting with the appropriate reagents. For example, the starting starch material may be initially phosphorylated or contain other cationic, anionic or nonionic groups, and may thereafter be reacted to introduce therein the anthranilate group.

Preferred starch anthranilates have a D.S. (degree of substitution) ranging from about 0.01 to about 1.0, and most preferably ranging from about 0.02 to about 0.3. The degree ,of substitution is an average figure, and conventionally employed to characterize starch derivatives. in essence, the degree of substitution sets forth the average substitution of each individual anhydroglucose unit present in starch, and is a conventional way of expressing the extent to which the anhydroglucose unit is reacted, or esterified in this particular instance.

One excellent way of making the starch anthranilates of the invention is by reacting starch with isatoic anhydride. This reaction may be carried out in the presence of a wide number of solvents utilizing a number of different catalysts. For example, the starch may be reacted with isatoic anhydride in dimethyl sulfoxide solvent using triethylamine as a catalyst. The following example illustrates a typical mode of preparation of a starch anthranilate.

EXAMPLE I A mixture of 40 g. (0.25 mol) of starch (dried overnight at 100 C.), 4.0 g. (0.025 mol) of isatoic anhydride, 5 ml. (0.036 mol) of triethylamine and 500 ml. of dimethyl sulfoxide was stirred at -95 C. for 3 hours in a flask protected from atmospheric moisture. The light brown solution was left overnight at room temperature and then poured into 1 liter of methanol. The precipitate was washed thoroughly with methanol in a blender and air dried to give 45 g. of white powder containing 10.4 percent moisture. An anhydrous sample contained 0.75 percent nitrogen corresponding to a degree of substitution of 0.093. Yields was 93 percent of theoretical.

Likewise the starch can be reacted with isatoic anhydride utilizing water as a dispersing medium. The following example illustrates a synthesis of this type.

EXAMPLE 11 To a well-stirred slurry of 90 g. of corn starch in 250 ml. of water was added over a period of 30 minutes 8 g. of isatoic anhydride and sufficient 6 percent solids sodium hydroxide solution to maintain the pH at 8.5-9.0. The alkali was added in various increments over a 2 hour reaction period to maintain the pH within this range. The reaction mass was then filtered, the solid washed with 2 liters of water, air dried and then continuously extracted with ethanol in a Soxhlet extractor for 24 hours. The product contained 0.70 percent nitrogen corresponding to a D.S. of 0.086.

The same type of reactions as shown above with respect to corn starch may be carried out with a number of different starch materials. The example below illustrates this.

EXAMPLE Ill The procedure of example [1 was essentially followed with the exception that waxy milo starch instead of cornstarch was the starting starch material acted upon. Specifically 92 g. of waxy milo starch and 8.15 g. of isatoic anhydride were mixed and reacted as set out in example 11. The produce contained 0.73 percent nitrogen corresponding to a D.S. of 0.090.

in order to determine the retention activity of the starch anthranilate it was evaluated according to established TAPPl Test T413. ln brief, titania in the amount of 10 percent by weight of the pulp, and alum were added to a bleached sulfite pulp which was then adjusted to the desired pH. A blank was then run whereby the pulp furnish was transferred to the head box of a Noble and Wood sheet machine where a series of nine sheets were formed continuously, pressed and dried. The white water which was drained into a holding tank was recirculated to the sheet-making machine during the formation of the nine sheets. The sheets were then reduced to ash at approximately 1,700 F. for 2 hours and the percent ash remaining was then measured. Sheets, 3, 5, 7 and 9 were then averaged to give a consistent picture of the percent ash remaining. Like sheets were made utilizing the starch anthranilate retention aid. Of course, the higher the ash total, the greater the retention ability of the additive. The starch anthranilate retention ability of the additive. The starch anthranilate retention aid was added in an amount of 0.5 percent by weight to the pulp furnish containing titania and alum, and sheets were made by the same method as in the above blank run. Results are shown below in table 1.

TABLE I Pigment Retention Composition Percent Titania Retained Blank 4 4 Starch anthranilate The starch anthranilate retention aid also showed surprising activity in increasing tensile strength and dry strength whether titania pigment was added or not. The dry strength was measured according to TAPPI method T403m53 and the tensile strength evaluated according to TAPPI method T404m50. Results are as follows.

TABLE II Strength Improvement (ln Absence of Added Pigment) The procedure of example Ill is followed except that in making the paper sheets different amounts of starch anthranilate are added to the pulp as follows:

0.] percent by weight(2 lbs/ton of pulp) 0.5 percent by weight-( l lbs/ton of pulp) 0.75 percent by weight( lbs/ton of pulp) 1 percent by weight lbs/ton of pulp) In each instance, the pigment retention is improved over a paper without the starch anthranilate additive and the tensile strength is as good or better when the additive is used.

The retention aids may be added at almost any step in the normal mill process, but it is greatly preferred that they be added subsequent to the refining step. The most preferred site of addition is at the headbox. Another practical application point is at the fan pump where the pulp is simultaneously finally diluted with white water to the proper consistency and pumped to the head box. The retention aids may also be added after the fiber is beaten and before the refining step, although this is a less preferred practice, with the effectiveness of the starch anthranilate being somewhat destroyed through subsequent agitation and refining steps.

The starch anthranilate additives have found use in increasing retention of nearly all types of inorganic fillers and fiber fines. Particularly their retention action is apparent when such fillers as either naturally occurring materials, e.g., talc, agalite, pearl filler, barytes, and certain clays such s china clay, or artificial fillers, e.g., suitably precipitated calcium carbonate, crown filler (pearl hardening), blanc fixe, and titania dioxide pigments are added to the pulp slurry. Inorganic color pigments and kaolin clays are also efficiently retained upon the fibers by use of the starch anthranilate. Retention activity of the starch anthranilate is improved through the use of alum, but it is understood, of course, that the starch anthranilate shows excellent activity even in the absence of alum.

Through use of the starch anthranilate, excellent retention of fiber fines and fillers may be realized in both Fourdrinier and cylinder paper machine systems. Increased filler retention realized from the use of this compound results in a brighter sheet with better density, opacity and ash content. Also better sheet formation, smoothness, printability and porosity are noted when the starch anthranilate is employed. As well, there is evidenced a greatly reduced two-sidedness, that is, dif' ferences of such properties as color and brightening of the respective sheet sides due to uneven pigment retention. In addition to the above advantages, use of the retention agent results in cleaner machine operation and a less abrasive system, reduced load to the save-all and minimal sewer losses due to the decrease in clay and white water solids. A particular desirable result realized through the use of the starch anthranilate is a decrease in pinholes in the paper sheet with a resultant improved paper product.

While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

I claim:

1. A method of improving the retention of inorganic filler and fiber fines in he processing of paper and of improving other paper properties which comprises adding to paper pulp, starch anthranilate, having a degree of substitution from about 0.01 to about L0, in an amount from about 0.1 percent to about 1 percent weight of the pulp, forming a paper mat, and drying said mat.

2. The method of claim I wherein the degree of substitution is from about 0.02 to about 0.3.

3. The method of claim 2 wherein the paper pulp also contains a sufficient amount of alum to improve the retention of the inorganic filler and fiber fines.

4. An aqueous suspension comprising paper pulp, an amount of filler for the pulp sufficient to impart a smooth surface, more brilliant whiteness, improved printability and improved opacity to paper made from the pulp, and starch anthranilate, the starch anthranilate having a degree of substitution from about 0.01 to about 1.0 and being present in an amount from about 0.1 percent to about I percent by weight of the pulp.

5. A suspension in accordance with claim 4 wherein the degree of substitution of the starch anthranilate is from about 0.02 to about 0.3.

6. A suspension in accordance with claim 4 wherein the suspension also contains alum in an amount sufficient to improve the retention of the filler.

7. A filled paper made form an aqueous suspension comprising paper pulp, an inorganic filler for the pulp in an amount sufficient to impart a smooth surface, more brilliant whiteness, improved printability and improved opacity to the paper, and starch anthranilate having a degree of substitution from about 0.01 to about 1.0 and being present in an amount from about 0.1 percent to about 1 percent by weight of the pulp.

8. A paper in accordance with claim 7 wherein the degree of substitution of the starch anthranilate is from about 0.02 to about 0.3. 

2. The method of claim 1 wherein the degree of substitution is from about 0.02 to about 0.3.
 3. The method of claim 2 wherein the paper pulp also contains a sufficient amount of alum to improve the retention of the inorganic filler and fiber fines.
 4. An aqueous suspension comprising paper pulp, an amount of filler for the pulp sufficient to impart a smooth surface, more brilliant whiteness, improved printability and improved opacity to paper made from the pulp, and starch anthranilate, the starch anthranilate having a degree of substitution from about 0.01 to about 1.0 and being present in an amount from about 0.1 to about 1 percent by weight of the pulp.
 5. A suspension in accordance with claim 4 wherein the degree of substitution of the starch anthranilate is from about 0.02 to about 0.3.
 6. A suspension in accordance with claim 4 wherein the suspension also contains alum in an amount sufficient to improve the retention of the filler.
 7. A filled paper made form an aqueous suspension comprising paper pulp, an inorganic filler for the pulp in an amount sufficient to impart a smooth surface, more brilliant whiteness, improved printability and improved opacity to the paper, and starch anthranilate having a degree of substitution from about 0.01 to about 1.0 and being present in an amount from about 0.1 to about 1 percent by weight of the pulp.
 8. A paper in accordance with claim 7 wherein the degree of substitution of the starch anthranilate is from about 0.02 to about 0.3. 